The present study was carried out at the Experimental Farm, Faculty of Agriculture, Menoufia University, Shebin El-Kom, Egypt during 2019 and 2020 summer seasons to study the influence of intercropping three summer grass forage crops, i.e. pearl millet, sudan grass and teosinte at 100% from their recommended seeding rate with maize at three densities of maize, i.e. 50, 75 and 100% of the recommended plant density (24000 plants/fed) on their productivity and quality as well as the land use efficiency and the competitive relationships. The treatments were arranged in a randomized complete blocks design with four replications. The obtained results could be summarized as follows: 1-Intercropping forage crops with maize decreased most growth characters (No. of shoots/m 2 , total chlorophyll, No. of leaves /shoot, leaf area/shoot and total dry weight/shoot, forage yield (fresh and dry forage yields/fed), chemical composition (protein% and ash %) as well as nutritive value (digestible protein "DP" % and total digestible nutrients "TDN" %), but increased plant height and fiber % of forage crops compared to their sole croppings. Sudan grass surpassed other forage crops in plant height and fiber%, while millet crop recorded the highest values of No. of shoots/m 2 , total dry weight/shoot, fresh and dry forage yields/fed. Teosinte crop exceeded millet and sudan grass in total chlorophyll, No. of leaves/shoot and leaf area/shoot as well as chemical composition (protein % and ash %) and nutritive values (DP% and TDN %). Increasing plant density of maize from 50% to 100% intercropped with forage crops increased plant height of forage crops, but caused a reduction in growth characters, forage yield as well as nutritive values of forage crops. 2-Intercropping maize with forage crops decreased yield and its attributes of maize (No. of ears/plant, No.of grains/ear, 100-grain weight, ear weight, grain yield/plant, grain and stover yields/fed, protein % and carbohydrates % in grains of maize, but increased oil %. Moreover, increasing plant density of maize up to 100% intercropped with forage crops increased grain and stover yields/fed as well as oil %, but decreased grain yield/ plant and its attributes, protein and carbohydrates % of maize. 3-The aggressivity results showed that the values of maize were positive (dominant), while the values of the three fodder crops were negative (dominated). Increasing the plant density of the maize from 50% to 100% intercropped with fodder crops also led to a decrease in the aggressivity value of the maize. The value of the competitive ratio for maize was greater than that of fodder. Increasing plant density of maize led to a decrease in the competitive ratio for maize but an increase in the competitive ratio for fodder crops. The values of the relative crowding ratio and land use efficiency were increased more than one compared to sole cultivation. The best intercropping system for obtaining the highest grain units was obtained when 100% maize was intercropped with millet or teosinte.
